## Name

ST_Quantile — 计算样本或总体上下文中栅格或栅格表覆盖范围的分位数。 因此，可以检查某个值是否位于栅格的 25%、50%、75% 百分位处。

## Synopsis

`SETOF record ST_Quantile(`raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] quantiles=NULL`)`;

`SETOF record ST_Quantile(`raster rast, double precision[] quantiles`)`;

`SETOF record ST_Quantile(`raster rast, integer nband, double precision[] quantiles`)`;

`double precision ST_Quantile(`raster rast, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, boolean exclude_nodata_value, double precision quantile=NULL`)`;

`double precision ST_Quantile(`raster rast, integer nband, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, integer nband, boolean exclude_nodata_value, double precision quantile`)`;

`double precision ST_Quantile(`raster rast, integer nband, double precision quantile`)`;

## 描述

 如果` except_nodata_value` 设置为 false，还将对没有数据的像素进行计数。

## 示例

```UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
--Example will consider only pixels of band 1 that are not 249 and in named quantiles --

SELECT (pvq).*
FROM (SELECT ST_Quantile(rast, ARRAY[0.25,0.75]) As pvq
FROM dummy_rast WHERE rid=2) As foo
ORDER BY (pvq).quantile;

quantile | value
----------+-------
0.25 |   253
0.75 |   254

SELECT ST_Quantile(rast, 0.75) As value
FROM dummy_rast WHERE rid=2;

value
------
254
```
```--real live example.  Quantile of all pixels in band 2 intersecting a geometry
SELECT rid, (ST_Quantile(rast,2)).* As pvc
FROM o_4_boston
WHERE ST_Intersects(rast,
ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
)
ORDER BY value, quantile,rid
;

rid | quantile | value
-----+----------+-------
1 |        0 |     0
2 |        0 |     0
14 |        0 |     1
15 |        0 |     2
14 |     0.25 |    37
1 |     0.25 |    42
15 |     0.25 |    47
2 |     0.25 |    50
14 |      0.5 |    56
1 |      0.5 |    64
15 |      0.5 |    66
2 |      0.5 |    77
14 |     0.75 |    81
15 |     0.75 |    87
1 |     0.75 |    94
2 |     0.75 |   106
14 |        1 |   199
1 |        1 |   244
2 |        1 |   255
15 |        1 |   255
```